1. Technical Field
The present invention relates to a static compensator and a method for controlling thereof.
2. Background
Voltage control of a general static compensator (STATCOM), which is a main function, is conducted by an output voltage control using an inverter itself. However, such a static compensator always has to have the capacity to control stabilization inside the static compensator in case of breakdown when it performs a stabilizing control function at the same time. It means that the performance of voltage control function of the static compensator causes a severe reduction in the capacity to control stabilization (reactive power output quantity).
A conventional static compensator has concentrated on operating for either automatic voltage control or power system stabilization control in accordance with characteristics of a power system. For example, if a power system has a problem of low voltage generation due to long-distance line or overload, a reactive power compensation function of a static compensator is emphasized. On the other hand, if a power system has a problem of voltage stability or transient stability, a power system stabilization function is emphasized in case of breakdown. Such problems limit the operation of a static compensator.
When the automatic voltage control of the static compensator is emphasized, it may have severe changes in the reactive power output margin quantity for an instantaneous stabilization control because it changes a reactive power output quantity to maintain a constant voltage of a power system.
On the other hand, when the stabilization control of a power system is emphasized, it is difficult for a static compensator to secure enough margin for a reactive power capacity to perform automatic voltage control of a power system and operate instantaneously in case of breakdown at the same time.